Coil system



April 2, 1940. w. L. DUNN coir.- SYSTEM Fild Jan. 11, 19:57

2 Sheets-Sheet 1 w Wm uwn Dun. LE

ts-Sheet 2 Patented Apr. 2, 1940 COIL SYSTEM WilliamLDunn,

Chicago,

Ill.,a-ignorto Belmont Radio Corporation, a corporation of IllinoisApplication January 11, 1937, Serial No. 120,047

4 Claim.

This invention relates to coil systems for radio 'eceiving sets or thelike, and particularly to such :01] systems as are adapted to beconstructed leparately for inclusion in a radio set as a unit. ['heseunits have been illustrated as including nductively coupled coilstogether with trimmer :ondensers therefor, connecting lugs for con-:ecting said coils to other parts of the circuit, ind a base adapted tohave mounted thereon any me of a variety of different coil structuresand :he condensers and connecting lugs for each.

All of the features of this invention are of gen- :ral utility, but someof them are of especial value in connection with the so-called multibandradio receivers. In such receivers it is common practice to provide oneor more primary coils and a different secondary coll for each band ofwave lengths or frequencies which the receiver ls designed to receive.If all of these coils are mounted into a single unit, the entire unitmust be rejected when one coil thereon is defective, and hence thenumber of rejects is relatively large. There would be the fewest numberof rejects if each secondary with its primary formed a separate unit sothat one unit could be rejected without the others. This results inexcessive material costs, however, and the most economical arrangementtherefore is to place the coils for at least two bands in a single unitwith the result that in a three-band receiver, two units will benecessary.

In order to keep the material and production costs as low as possible,and yet maintain a highly eillcient operating level for the coil system,it is necessary in such coil systems for the multiband receiver toconsider not only the question of rejects of coil units, but theassembly of the units themselves, the assembly of the entire coilsystem. and particularly the actual testing and inspection operation.

In most eiiiciently taking care of all these factors, there was theproblem of providing all elements of the system capable of rapidassembly into units and into the coil system. providing them to performas many functions in the complete apparatus as possible. and at the sametime eliminating or minimizing undesirable capacities, and inductancesin the circuit of the coil system. as well as having those elements actto speed up inspection and reduce breakage and reiects. Inasmuch asvariations in the particular coil assembly might be necessary for eachband of each particular type of multi-band receiver, itwasdesirabletohaveauniversalbaseof insulating material which would take anyone of such various assemblies. The connecting leads in high frequencycircuits may introduce an appreciable and undesirable inductance in thecircuit, and it was therefore desirable to have connecting leads in thecomplete coil system as short as possible. While it was desirable toprovide variable capacitors across each secondary of the coil system toadjust the circuit capacity at the high frequency end of the bands to auniform value, it was likewise necessary to maintain stray capacity ofall components to ground in the entire coil system at a minimum. Inproviding terminal members both for general wire connection, and for thevariable capacitors of metal in a stamped out construction extendingthrough the assembly base, undesirable inductance and circuit capacityis minimized, while the single shield of large perimeter of the presentinvention, has the most beneficial effect so far as the coil dissipationconstant is concerned. Where previously in making inductance testsparticularly, on coils, one or more wire ends were placed into springcontacts in the testing jig, the present construction now makes itpossible to eliminate this added handling and danger of breaking wires,inasmuch as the lugs alone effect all the necessary circuit connectionsin the jig.

According to the present invention, therefore, the receiver is providedwith two detachable bases, each adapted to have a coil unit mountedthereon, but in the interests of economy these bases are identical, andin the interests of ease of mounting, each of them is secured to thechassis by a single screw. It is understood, of course, that more thantwo bases may be employed as the system is adapted to receivers ofincreasing numbers of wavebands. The coil system of the presentinvention, as illustrated and described, provides a completecoil'assembly sufflcient for at least a four-wave band receiver circuit,all covered by a single shield. This single shield has the doubleadvantage of reducing material costs and increasing the coil dissipationconstant which in general is increased as the perimeter of the shield isincreased. Furthermore, the coils themselves are small piwsically withrelation to the shield, thereby increasing the spacing between the coilcomponents and the shield, and reducing the stray capacity at this pointto a minimum.

Since the base is to be identical for different coil units, it is formedwith suitable apertures for mounting thereon, any one of severalspecifically different coil assemblies and associated terminal elementsas such unit. This of course is desirable whether two different unitsare to be used in one set or not, so that the same base may be used withdifierent coil structures even in diiferent receivers. In using twoidentical bases in juxtaposition in one set, there is a special problemin providing compactness of arrangement together with ease of mountingthe bases to the frame. For compactness it is of course desirable tohave a single cut-out opening through the chassis, at which opening boththe bases are to be secured; and it is likewise desirable that the basesfit snugly against one another, and that no space within the opening bewasted. Accordingly, the identical bases are made with the securingaperture at one side thereof, and one of the bases is inverted forassembly of the elements on it so that the securing holes are positionedat the far sides of the two bases as used, thus making it possible tomount the two coil units against the receiver chassis frame at the edgesof the bases while lugs on the bases extend through a hole in thechassis under which the coil units are positioned.

A very important feature of the present invention, both from thestandpoint of convenience in connecting the coils with the externalportions of the receiving circuits and from the standpoint of minimizingstray capacity and other losses, is the provision of connecting lugswhich are secured to the base and extend therethrough so that theexternal wires may be connected on either side of the base, rather thanextend through the base. This feature is utilized throughout the coilunits including the lugs on the individual coil forms, the trimmercondensers and the separate connecting lugs. One reason it is importantto minimize stray capacities is to obtain reception over any desiredrange of frequency with the smal'est possible number of coils. The useof a large shield encircling the coil system contributes to this result.

Inasmuch as the trimmer condensers and connecting lugs pertaining toeach coil form are mounted on the base to which that form is se- 1cured, the coils may be connected thereto before assembly of the unitsin the receiving sets. Furthermore, because of the fact that thestandard perforations of the base insure uniformity of positioning oithe connectors with each type of coil unit, testing of the coils isgreatly facilitated by virtue of the fact that a testing jig may beprovided with spring contacts for each corresponding aperture in thebase so that it is merely necessary to place the entire coil unitthereon and the proper test connections will be automatically connected,depending on the particular terminal arrangement in the apertures onthat base.

The objects of the invention are mostly apparent from the foregoingdescription of the special features and advantages. Further objects andadvantages will be apparent from the fol lowing description and from thedrawings, in which:

Fig. 1 is a horizontal sectional view of the form of this inventionchosen for illustration, showing a plan view of the coil assemblies insubstantially twice actual size.

Fig. 2 is a bottom view of the structure shown in Fig. 1.

Fig. 3 is a vertical sectional view showing the coil assemblies inelevation.

Fig. 4 is a fragmentary sectional view of one of the connecting lugs.

Figs. 5 and 6 are fragmentary sectional views taken respectively on thelines 5-! and 8-4 of Fig. 2, and showing the trimmer condensers.

Figs. 7, 8 and 9 are views indicating the manner of forming respectivelythe connecting lugs, the fixed condenser plate, and the movablecondenser plate from single pieces of metal.

Figs. 10 and 11 are fragmentary circuit drawings showing the connectionsprovided in the coil assemblies; and

Fig. 12 is a view of a modified embodiment illustrating fragmentarily acoil system with more two coil units.

Although this invention may take numerous forms, only one has beenchosen for illustration. In this form, the invention has beenillustrated as associated with a frame or chassis l I of a radioreceiving set. This chassis is provided with an opening l2 therethroughof generally rectangular shape. Securing lugs II on the chassis mayproject into the general outlines of the opening l2. A pair ofinsulating bases II and HA are secured below the chassis II by means ofscrews I6 passing through suitable perforations in the bases l4 and HAand threaded into the securing lugs [3.

Above the frame H a shield I8 is secured, this shield surrounding theentire opening I2 and consequently substantially the entire areas of theinsulating bases. The shield may conveniently be secured by means of apair of securing studs riveted thereto and passing downwardly throughthe frame II and through holes formed between the two bases H and MA asshown at is. These last mentioned holes may be formed by the provisionof semicircular notches in the edge of each base. The shield i8 may beprovided with an aperture 2i at the top thereof through which a gridclip 20 (Fig. 3) may be passed for connection to a tube requiring anexternal top connection.

From Figs. 1 and 2 it would appear at first glance that base H and baseA are different, one being adapted to fit at the left-hand side of theopening I2, and the other at the right-hand side thereof, as seen inFig. 1. As a matter of fact, however, these bases are identical, thenecessary result being obtained by positioning them with their oppositefaces up, thus making it possible to stamp out only a single form forall bases, yet use them either for the coil unit for the right side, orthat for the left side in the two-unit assembly of Fig. 1.

A modified embodiment is illustrated in Fig. 12, in which more than twocoil units are provided in the complete coil system. Identical bases Bare mounted at an opening in a chassis H by means of screws throughholes at the top and bottom of each base B extending into mounting lugsl3 on the chassis at the opening. Coils C, D, E, F, with one mounted oneach base, are illustrated somewhat diagrammatically. It is understoodof course that the number of individual coil units may be varied inaccordance with the number of wave bands for which the receiver isdesigned.

From Fig. 3 it will be seen that two different coil forms are provided.As a matter of fact, there may be several other forms than those shown.In general, however, they will comprise a solid dowel 23 which may beeither of ceramic material or wood, on which coils 24 and 25 are wound,or a tube 26 on which coils 21, 28, 29 and 3|! may be wound. The soliddowel such as 23 may be secured to the base It (or HA) very easily bymeans of a screw 32 passing through hole II in the base and screwinginto the bottom 7| 0,198,, I g I I w 3 of the dowel. To prevent thedowel from turn-- ing, a lock washer 33 may be desirably positionedbetween it and the base I4, and for that purpose the base It is providedwith small apertures 34 into which special projections on the lockwasher may flt. while projections in the opposite direction project intothe dowel.

The tubular coil form 2| may be secured in a somewhat similar manner(not shown) by hav- 9 ing its lower end flanged over and a washerinserted down through the tube 20 to be secured to the base by a screwor by an eyelet. However, it is preferred inaccordance with thisinvention, to provide the tube It, which may be formed of w anydesirable insulating material, with a plurality of combined connectionand attachment members 36 secured to the lower end of the tube. Thesemembers 38 include flat connecting and securing lugs 31 projectingdownwardly from the I) tube 26 and through correspondingly shapedapertures a in the base A. The lower endsofthelugsllaretwistedtostandinaplane crosswise of the apertures it as seen in .Fig.2soastobindthelusstheslotsand Ilockthetubeflinplaceon lugs also facilitate testing ofthecoll before is assembled on a base It or they will slip directly intospring contacts in a testing jig. The members It also includeoutstanding lugs It so that connections can be made to them above thebase A as well as below.

l 'roml igslandzitwillbenotedthat grouped around the securing hole 3|ofeach base (i. e. around the coil forms) are a plurality of It pairsofaperturesinthebase,eachpai rincluding a small slot, ll and a circularopening 4!.

These are provided for connecting lugs, some of which have been shown inplace. These connecting lugs each include an upstanding solderm ing lug46, a downwar ly extending soldering lug l1, and a securing base 48, ofwhich ajportion is extruded to form an integral eyelet 40. In thepreferred form of the invention, the soldering lug 46 extends through aslot 4|, while will be apparent that by bending the soldering lug 46 inone direction and the soldering lug 41 in the other direction aboutthedotted line Ii, the finished connecting member will be formed.asshowninl"ig.4,whichalsoshowshowitis securedtothebasellbyupsettingtheeyeletll. Bothofthesesolderinglussmaybeprovided withperforations I! to facilitate securing a wire thereto, if desired.However, the soldering lug l'lmaybeshortenedasatl'l'inFigJtoomit theperforation 52. In this case the projections 63 formed by 'cutting outthe lug 46 will tend to help hold the wire in place during soldering.

As seen in Figs. and 11, atrimrner con- 53 denser 56 is desirablyconnected to each ofthe secondary coils 25, 21 and 20. Thus, on the baseA, on which two of the secondary coils are mounted, there will be twotrimmer condensers whileonthebase Iltherewlllbeonetrimmer m condenser.Since two trimmer condensers will be desired on some bases, the basesare still provided with suitable perforations for these condensers,these perforations being those shown in the lower portion of Fig. 1. nThe structure and eat of the condensersisshownbestinl'igsJandfiwithrefqerence also to Figs. 8 and 9. h denser plates is stamped out of a singlesheet of metal, as seen in Figs. 8 and 9. condenser plate Cl is providedwith a securing s aperture 02 through which a rivet is passed to secureit to the base It or "A by a rivet 03. It is also provided with lugs 64and 5 which are respectively bent upwardly and downwardly about thedotted lines 80. The upwardly bent to lug 84 passes through a slot inthe base It, thus determining with the rivet 83 the position of theplate II and preventing rotational movement of the plate, and alsofurnishing a soldering lug above the base ll.

The movable plate II is of a more complicated structure, being providedwith the integral resilient loops I2 bent from the plate II at thedotted line II. At the far ends of the loops 1! a transverse web ll isprovided from which is bent a securinglug 'llwhichisflrmlysecuredtothebase II by a rivet 16. The loops I: are continued to form lugs 11 whichboth pass upwardly through slots in the base It and together with rivetit properly position and hold the conas denser plate II on the base.

Theloops'llareresilientandbiasedinadirection to move the plate ll awayfrom the plate II. a mica plate II or ,any other good dielectricinsulatingly separates the two metal plates and so is retained againstthe fixed plate 8 by the rivet CI therethrough and the rivet ll securingthe movable plate II on the base (Figs. 5 and 8). Plate II is movedtowards the plate I for adjustment of the capacity of the condenser by a88 screw It passing through a hole II in condenser plate II. An enlargedhole 82 is provided in fixed condenser plate ii so that it will not makecontact with the screw II, which screws into the base ll. The plates IIand II are of course receaed wherever to prevent contact with the rivetsfor and connected with the other plate,such beingseenat8landfl.

Fromtheforegoingitwillbeseenthateach condenser plate has at least onecontact above thebase l4 andonebelomandthatallofthe' other connectionmembers are likewise provided with a connecting portion above and aconnectingportionbelowtheplates.ThismakesitentirelyunnecessarytohaveanywiresextendingthroughthebasellorllAandhence'thecom'stantsofthecoilscanbepredetermincdveryaccuratelysincethecoilsmayalwaysbeconnected to connecting lugs withminimum lengths of wire positioned entirely above the bases, thus 5preventing excessive inductances in the current due to long leads. Infact, in some instances, as at A (Fig. l), the lugs are of such length,and so positioned, that two lugs may be solderedtogetherratherthanrunawirefromonetothe other. At connection A 9. lug 84from the sta- 'tionary plate of a trimmer condenser isconnectedtoalugflc rryinsaleadfromthecoil 21. The wires connecting thecoil assembly with external portions of the circuit will usually be 65connected below the bases, and of course a band selector switch will beprovided for connecting the coils to be used.

Although the invention has been described in its preferred embodiments,it is understood that various specific coil assemblies and systems maybe provided, all utilizing the present invention, and it is not limitedthereby but is limited only by the scope of the appended claims.

I claim:

1. In a radio receiving set, a chassis having a relatively large openingtherethrough, a pair 01 identical bases differently disposed withreference to one another secured to said chassis at said opening bysecuring means at an outer edge of each base and having formationstherein for mounting parts of a coil system on the portions of the baseswhich are exposed through said opening, with said bases being mounted atsaid opening with an inner edge of each in abutting relation but withthe securing means therefor being such that each base is mountedindependent of the other and a separate coil form together withconnecting means for all terminals of the coils thereof mounted on eachof said bases whereby each of said units including coil form,connectors, and base, may be accepted or rejected and replacedindependently after test.

2. In a radio receiving set, a chassis having a relatively large openingtherethrough, a pair of identical bases difierently disposed secured tosaid chassis at said opening at an outer edge of each base and havingformations therein for mounting parts of a coil system on the portionsof the bases which are exposed through said opening, with said basesbeing mounted on said chassis in edge to edge relation but independentlyof one another, a separate coil form together with connectors for allterminals of the coils thereof mounted on each of said bases wherebyeach of said units including coil form, connectors, and base, may beaccepted or rejected and replaced independently after test, and a shieldsurrounding both of said coil forms and secured to said frame.

3. Apparatus of the character described including in combination a metalradio receiving chassis having an aperture therein and a coil systemsecured to said chassis at said aperture comprising a pair of insulatingbases positioned in abutting relationship at one edge of each base, andsuch bases together having a. perimeter greater than the aperture insaid chassis so as to over lie the aperture and extend together beyondthe edge of said aperture whereby to be supported on said chassis atsaid aperture edge, each of said bases adapted to be secured directly tosaid chassis adjacent the aperture with thesecuringoteachbeingatapointspacedfromthe abutting edge, a coil mountingsupported on each insulatingbaseandacoilonssidmmmting,a condensersecured to each base, contact means for said condenser extending to eachside of said base for electrical connection with said coil on one sideand for receiving on the other side electrical connections from theradio receiver, with said two bases with the elements thereon beingindependently mountable and removable so that each base with itsassociated elements may be assembled, tested, and serviced independentof the other, and a single shield surrounding the elements on said twobases having means thereon for securing said shield to said chassis atsaid aperture with said securing means acting to also secure saidinsulating bases to said chassis.

4. ,Apparatus of the character described including in combination ametal radio receiving chassis having an aperture therein and a coilsystem including a pair of coil units secured to said chassis at saidaperture, each of said coil units including an identical insulating basehaving a coil mounted on one side thereof, contact lugs for said coilhaving portions extending entirely through said insulating base forreceiving wire connections on each side thereof, with the wireconnections on one side extending to said coil and on the other sideextending to radio receiver apparatus on said chassis, with the base ofsaid coil units being positioned in edge to edge rela tionship andtogether having a perimeter greater than the aperture in said chassisand overlying said aperture whereby to be supported on said chassisbeyond the aperture edge, a single shield member for mounting over saidpair of coil units and adapted to be secured to the chassis, securingmeans for said shield extending through said insulating bases at theirabutting edges and actingto secure said basestosaid chassis aswell assecure said shield to said chassis, and the assembly oi the structureand connections on each base being such as to permit the assembly on andthe removal from said chassis of each coil unit independent of the othercoil unit.

WILLIAM L. DUNN.

